In 3GPP wireless technologies, for example Global System for Mobile communications (GSM), Universal Mobile Telecommunication System (UMTS), and Long Term Evolution (LTE), the Radio Resource Control (RRC) protocol handles the control plane signalling of Layer 3 between the UEs (User Equipment) and the Radio Access Network (RAN), i.e. the network residing between the UEs and core network. In UMTS, the RAN comprises the NodeBs and Radio Network Controllers (RNCs).
The RRC protocols includes for example:                Functions for connection establishment and release,        Broadcast of system information,        Radio bearer establishment/reconfiguration and release,        RRC connection mobility procedures,        Paging notification and release,        Outer loop power control.        
In order to transmit/receive data to/from a mobile terminal such as a UE, the UE needs to have an established RRC connection. When in RRC connected mode, the UE may operate in different communication states. In 3GPP, these communication states are referred to as RRC states. FIG. 1 exemplifies the different communication states and the transitions between the states in a UMTS network, Inactivity for a certain time, which is determined by a timer, in a connected state generally results in transition to a less resource consuming state, while activity results in transition to a higher state in which more resources are required by the UE and the RAN. In general, communication states which provide the UE with a higher data rate require more resources, and vice versa, as is illustrated in FIG. 1. The signals used to effect transitions from one state to another are generally referred to as radio bearer re-configuration signals in UMTS, and radio bearer setup/release signals in LTE.
The configuration of RRC inactivity timers in UMTS (and in LTE) networks has great impact on resource consumption in the RAN and the UE, e.g. processing load and memory allocation in the radio nodes, UE power consumption, and radio resources. The RRC idle mode (i.e. no connection) results in the lowest power consumption of the UE. In UMTS, the states in the RRC connected mode are, in order of decreasing resource consumption, CELL_DCH (Dedicated Channel), CELL_FACH (Forward Access Channel), CELL_PCH (Cell Paging Channel) and URA_PCH (URA Paging Channel). The power consumption in the CELL_FACH is roughly 50% of that in CELL_DCH, and the PCH states use about 1-2% of the power of the CELL_DCH state. However, the transition of a UE between the different RRC states results in processing load in the radio nodes.
The transitions to less resource consuming states occur when inactivity timers trigger. Different operators have different configurations for the inactivity timers. The latency in the system also increases in the lower states; it takes some time to reach higher states. There is further a cost associated with communication state transitions, with respect to UE management undertaken by e.g. an RNC, a Base Station Controller (BSC), an eNodeB, etc., whichever of these network elements handles the transitions, implying that the inactivity timers are set such that it should be worthwhile to change the state.
In order to decrease power consumption in the UE and system resources in the radio access network, while the UE is in connected mode, there are functions like Discontinuous Reception and Transmission (DRX). The RAN determines, generally at setup, periods when the UE is permitted to turn off its transmitter or receiver, or both, in defined intervals when there is no data transmission. For example in a UMTS network, by allowing the UE to stay inactive in CELL_DCH state for longer time periods, the UE can restart transmission after a period of inactivity with a much shorter delay than would be necessary when switching state from CELL_FACH or URA_PCH or re-establishment of a new connection. This will also facilitate reduction of the number of state transitions between CELL_FACH, CELL_DCH and Idle.
Discontinuous Reception is also available in LTE networks where the period in the connected state normally is longer than in UMTS networks. In LTE there are two different modes of DRX, short and long DRX mode.